WiFi Wireless Fidelity

Wireless Fidelity.

Th Brand name “WiFi” is used by WiFi alliance to describe WLAN products which follow IEEE 802.11 specification. WiFi Alliance. “Wi-Fi CERTIFIED” is a brand name of WiFi Alliance. It ensures the devices of different vendors are inter operable. It works on Data link layer and physical layer

IEEE 802.11.

WiFi or WLAN use ISM (Industrial, Scientific and Medical) band in 2.4 GHz region. ISM band is used for licensed free wireless transmission. UNII (Unlicensed National information Infrastructure) band in 5 GHz range.

Project 802.

In 1985 IEEE started a project 802. Named for the year and month (’80 Feb). Its goal was to set standards to establish communication between devices. It defines a family of protocols at Data link and physical layers.

CSMA/CD and CSMA/CA.

CSMA / CD. It detects the collision and terminates the transmission immediately. It is mostly used in wired media where

CSMA / CA. It is more efficient than CSMA/CD. It detects the medium is free or busy. Transmitter waits until the medium is free. It is mostly used in wireless media.

Topology / Operating Mode.

Peer to Peer/Ad Hoc mode.

It enables devices to connect each other without the need of any central device or access point.

Client Server/Access Point/Infrastructure mode.

Devices are connected to access point. Access point performs the function of bridge between wire network and wireless network.

Architecture.

Wireless Station WSTA. A device that is connected to a WiFi network is called wireless station.It may be a PC, Laptop, Desktop, Mobile phone or etc.

Access Point AP. It is a device which connects multiple wireless stations.

Basic Service Set BSS. Basic service set is formed when two or more wireless devices are connected to the Access point AP.

Working.

MAC layer.

It is a sublayer of Data link layer. It controls the transmission across shared media. Its function in WiFi architecture is same as in ethernet architecture CSMA. Therefore, WiFi and Ethernet use the same format of MAC address.

Physical Layer.

It deals with the transmission of radio waves. ISM and UNII band are used for unlicensed radio transmission.

SSID Service Set Identifier.

AP broadcast its SSID in packet transmission. The client decides whether to connect or not on the basis of signal strength.